Counterbalanced armature for electromagnets



April 29, 1958 J. H HORMAN 2,832,921

COUNTERBALANCED ARMATURE FOR ELECTROMAGNETS Filed April 28, 1954 2 Sheets-Sheet 1 JNVENTOR.

(/0/7/7 H. Harman- BY M M fm i Alf/aways April 29, 1958 J. H. .HORMAN 2,832,921

COUNTERBALANCEDARMATURE FOR ELECTROMAGNETS Filed April 28, 1954 2 Sheets-Sheet 2 H65 F/G. 4

INVENTOR.

John H. Harman BY W w uw Af/omeys COUNTERBALAN CED ARMATURE FOR ELECTROMAGNETS John H. Herman, Tuckahoe, N. Y., assignor' to Allied Control Company, Inc., New York, N. Y., a corporation of New York Application April 28, 1954, Serial No. 426,220

11 Claims. (Cl. 317-195) This invention relates to an armature for solenoid type electro-magnets, and more particularly to a counterbalanced armature for an electromagnet. The invention is especially useful in its application to electromagnetic apparatus employed in airborne and other. equipment wherein it is subject to high inertia forces due to shock, vibration, and sudden acceleration or deceleration.

A familiar type of electromagnetic apparatus is one which acts to open or close contacts in an electric circuit, for example, a relay. Such apparatus includes a solenoidal coil and an armature movable within the coil when,

the latter is energized. A spring-biased member is moved by the armature, when the. coil is energized, to open or close the electric contacts. In single-coil electromagnets of this type, the armature is held in inoperative position by a spring, the force of which is overcome by energization of the solenoid to operate the apparatus. If the force of the holding spring is slight, sudden acceleration or deceleration of the apparatus axially of the solenoid may move the armature to open or close the electric contacts unintentionally. If the force of the holding spring is strong enough to prevent this, then a substantial electrical force is required to operate the apparatus.

The present invention provides a counterbalanced armature which is immune from the forces of gravity and inertia. Thus, only a very light holding spring is required, or possibly only the spring force in the contacts themselves in a relay, and a relatively small electrical force suifices to move the armature and operate the apparatus.

According to the invention, the counterbalanced armature comprises two members, at least one of which is of magnetic material, the other preferably, though not necessarily, of non-magnetic material, and a centrally supported lever connected at one end to one member and at its other end to the other member. Accordingly, as one member moves in one direction the lever is rocked about its central support and moves the other member oppositely. The two members having substantially equal moments of inertia (mass times lever arm), they counter balance one another, and no gravitational or inertia forces displace the armature to operate the apparatus unintentionally.

The invention will best be understood from the following detailed description of the presently preferred embodiment of the invention, taken in conjunction with the drawings, in which:

Fig. 1 is a vertical mid-section through an electromagnetically operated switch mechanism in which a counterbalanced armature according to the invention is embodied, the electromagnet not being'energized;

Fig.2 is a similar section, the electromagnct being energiz'ed;

Fig. 3 is an enlarged vertical mid-section through the counterbalanced armature shown in Figs. 1 and 2, the armature being shown in the position illustrated in Fig. 1;

Fig. 4 is a view similar to Fig. 3, the armature being shown in the position illustrated in Fig. 2; and

States Patent.

Fig. 5 is a cross-section taken on the line V-V of Fig. 3.

In Figs.- 1 and 2, there is shown an electromagnetically operated switch mechanism or relay similar to that described in the copending patent application of John H. Horman and Edward C. Hoell, Serial No. 273,962, filed February 28, 1952, for Electromagnetic Relay, now Patent No. 2,749,403.

In the present embodiment, the relay comprises a disc 10 which carries the electrical connections and switch contacts, and an electromagnet assembly 11 suitably fixed with respect to the disc. The disc 10 and the electromagnetic assembly are so related as to provide a space 12 therebetween for accommodation of the switch contacts, which the electromagnet assembly is positioned to separate when energized. A mounting ring 13 fixed to the relay provides means, through a perforated flange 14 thereon, for attaching the relay in required position,

as by a bolt 15.

The detailed construction illustrated in Figs. 1 and 2 1 is substantially that disclosed in the aforesaid copending patent application and need not be here particularly described. Obviously such construction may be varied as desired.

For purposes of illustration, only a single pair of switch contacts is shown. Thus, a fixed contact 16 is carriedi within the space 12 by a stem 17 extending through the 5 disc 10 and ending in a terminal 18 outside of the relay. Similarly, a coacting movable contact 19 is carried by a second stem 20 extending through the disc and ending in 1 a terminal 21; The movable contact is fixed to a U-sh-aped i conductive spring arm 22 fastened at one end to the second stem 20 and projecting beyond the movable contact 19 into the path of an actuating member, later to be described. As illustrated, the contacts are positioned to be: normally closed and opened by electromagnetic action... However, such is not necessarily the case. A third stem; 23 is shown to which one of the solenoid leads 24 is con-- nected, it being understood that there will be two such! stems and leads.

Each stem extends into the space 12 through a glass: or other insulating bushing which is fused into a hole in. the disc 10 and about the stem. Such bushings 25 and 26 are illustrated in Figs. 1 and 2 as surrounding the stems 20 and 23, respectively.

The electromagnet assembly comprises, essentially, a. solenoid 27 enclosed within a shell of magnetic material. consisting of two annular cup-shaped pole-pieces 27a and. 27b, the outer edges of which are flattened to closely engage one another as shown at 27c, and the inner edges; of which are spaced apart thereby providing in the shell. a gap 27d located within the solenoid, a pole-piece bushing 28 of magnetic material extending from the space 12. substantially half way through the solenoid within the pole-piece 27a and forming its fixed core, an actuator 29' of light rigid insulating material slidable axially in the pole-piece bushing, and the novel counterbalanced arms-- ture generally designated 30 disposed centrally within. the pole-piece 27b within the solenoid beyond the inner end of the pole-piece bushing. I

The actuator 29 is counterbored at one end to receive the end of a light coil spring 31 which is compressed be tween the disc 10 and the actuator to hold the latter away from the movable electrical contact spring 22-with its: inner end extending beyond the inner end of the polepiece bushing 28. In this position, a circumferential flange 32 on the actuator is held against the outer end of the pole-piece bushing.

The circumferential flange 32 projects over the freeend of the U-shaped spring arm 22. Thus a force applied. against the inner end of the actuator 29 moves the actuator axially in the pole-piece bushing 28 in opposition 3. to. the force of spring 31 to cause .the flange 32 to bear upon the free end of the U-shaped spring arm 22 and separate the contacts 16 and 19. Such force is applied by thenoVel counterbalancedarmature v upon energizatio n ofthe solenoid 27;

The counterbalanced armature 3d comprises a member, 33 of magnetic material, a second member34, whichmay or may no t beof non-magnetic material, and a leyer 35' movable about a virtual fixed pivot 36 and operatively connected to each of said members. In the presently preferred embodiment, the members 33 and 34 are in slidable Contact with each other and so are preferably ofclii'lerent metals to reduce wear, g. steeland brass respectively.

As best shown in Figs. 3, 4 and 5, a guide post 37, I

preferably of non-magnetic material, is suitably fixed as by threads in a fixed member of the relay to extend therefrom axially iuto the central space formed by its solenoid 27. The guide post has, at its end farthest from member 38, remain flattened tongue portionfi? having a hole 4% therein through which the lever 35 extends, and which provides its support or virtual fixed pivot. The hole 4 is outwardly tapered from its center to each end thereof, thus enabling the lever to rock or oscillate relative to the tongue 3? which serves as a fulcrum. Lever 35 is in the form of a cylindrical rod or pin, as illustrated.

The concentric members 33'and S t-fare elongated, hollow and tubular in form. Hence these members constitute a pair of telescoped coaxial cylinders which are connected together, as by the lever 35, for-simultaneous axial movement in opposite directions. Member 33 has a closed end 33' and is the movable armature of the electromagnet.

The member 34 is immediately slidable over the guide, post 37, which has annular flangesdl and d2 thereon in sliding contact with the inner face of member 34. The other member 33, of magnetic material, is formed to slide over theouter face of the inner member 34 with its inner face in contact therewith and its outer face in sliding contact with a cylindrical sleeve 43 of non-magnetic material positioned in the central space within the solenoid 27.

It i preferred remake the armature me nber 33 as a cylindrical cup in order that, when the solenoid isenergized, the bottom 33 of the cup may bear upon the inner end of the actuator 2% and separate the switch contacts in the manner already described. However, other constructions obviously might be employed for this purpose. Furthermore, the outer member 33 mightbe an open ended cylinder of non-magnetic material and the inner member 34 of magnetic material and act as the armature, and when so related, the latter member might be cupshaped and engage the actuator.

The lever is operatively connected to the members 33 and 3-; in very simple manner. For this purpose, a suitably positioned hole 44 is provided in the. wall of the outer member 33 and a corresponding hole 45h; provided in the inner member 34, both holes being of a diameter freely to receive an end of the lever 35. As here shown, both holes extend entirely through the respective members and are tapered outwardly of the members to permit the lever to oscillate or rock asdescribed' while maintaining close contact with the members. The described connections are necessarily loose because of the rectilinear movement of the hollow members and the arcuate movement of the lever ends.

A longitudinal slot 46 is formed in the inner member 34 diametrically opposite the hole 45 therein to permit the lever 35 to extend therethrough with its end in the hole 44 of the outer member. The effective lengths of thelever arms will, in the structure shown, be greater between its virtual pivot 36' and its hinged connection with the outer member 33 than between the pivot and its connection with the inner member 34. A slight increase in the weight of the inner member will, however, com- 4 pensate for such difference to produce equal counterbalancing effects.

It is to be noted that there is no need for a fixed physical pivot for the lever 35 in the form of a pin, trunnions or the like. The lever merely oscillates or rocks in the hole 49 about an axis or virtual pivot which is determined by the shape of the hole. Furthermore, the lever cannot move axially thereof because it engages the inner wall of the outer member 33 and the inner wall of the cylindrical sleeve 43 immediately outside of the holes 45 and 44, respectively.

From the foregoing itwill be recognized that, according to the invention, a balanced armature is provided wherein any assumed position of its members is maintained until one of the members is separately subjected to external force. The balanced structure makes it unnecessary to retain the armaturein normal position by-a' spring adequate to maintain that position under heavy inertia force's.

Accordingly, operatiouof the relay will be evident The electromagnet not being energized, the light coil spring 31 niovesthe actuator 29 inwardly of the solenoid,-

7 until its circumferentialpfiange 32. bears upon the; adjaccnt end of the pole-piece bushing 23 and the inner end of the actuator projectsbeyond the inner enc l of the bushing. In so moving, the actuator slides the member 33 of the counterbalanced armature 3t awayfrom the pole-piece bushing 28, and the member 34 moves toward, the bushing, The switch contacts 16 and 19 close, and, the elementsof the relay stand in the positions illustrated;

in Figs. 1 and 3.

Energization of theelectromagnet acts upon the mem-,

toward the disc10, against the action of thespring 31..

The actuator flangeGZ moves the free end of the U- shaped aimez to .openthe contactslo and19 (see Fig. 2). Clearly, other. contacts Wlil'lll1-tll6 space 12 may be opened or ,closed by such movement of the actuator flange 32 As. soonas the solenoid 27 is deenergized, the spring 31 easily movesthe actuator 29v andthe counter-balanced armaturefitlinto the positionsshown in Fig, l and the contacts 16 and 19 .close.

Becauseof the counterbalanced construction of the armature 3tl-and the small mass of the actuator 29 inertia forces produced i bysacceleration, deceleration, vibration or shock 'willnot ,open or close its contacts, and a stable relay isprovided. forusc in apparatus such as airplanes, guided mana r. the-like. Since the spring used to retract the armature andtohold it in-retracted position needv not withstand such inertial forces, the electrical.

power required tomoye the armature and operate the relay is minimized.

The form of the invention here particularly, described and illustrated in the drawings is presentedmerelyas. an example ofhow the invention may be applied. Other forms, embodiments and applications of the invention coming within theproper scope oi -the appended claims will readily suggest themselves to those skilled in the What is claimed is 1. A counterbalanced armature for an electromagnet comprising a pair of telescoped tubes, and a lever centrally pivoted within the tubes connecting said tubes together for simultaneous movement, in oppositedirections, at;le ast one of said tubes being of magnetiema: terial.

loosely connected to each cylinder, whereby said cylinders have simultaneous axial movement in opposite directions, at least one of said cylinders being of magnetic material.

3. A counterbalanced armature according to claim 2 wherein one of said cylinders is of non-magnetic material.

4. A counterbalanced armature according to claim 2 wherein said cylinders and the corresponding ends of said lever have substantially equal moments of inertia.

5. A counterbalanced armature for an electromagnet comprising a tubular member of magnetic material, a second tubular member of non-magnetic material in slidable contact with said first-named member, and a lever movable about a fixed central pivot and operatively connected to each of said members.

6. A counterbalanced armature for an electromagnet comprising an elongated hollow member of magnetic material, a second elongated hollow member coaxially and slidably related to said first member, and a lever movable about a fixed central pivot and operatively connected to each of said members.

7. A counterbalanced armature for an electromagnet comprising an elongated hollow member of magnetic material, a second elongated hollow member, one of said members being slidably fitted within the other of said members, a lever movably connected at opposite ends thereof to each of said members, and a fixed pivotal support for said lever within said members.

8. A counterbalanced armature for an electromagnet comprising a tube of magnetic material, a tube of nonmagneticmaterial, one of said tubes being slidably fitted within the other and having an ouutwardly tapered hole therethrouguh, the other tube also having an outwardly tapered hole therethrough, and a lever pivoted substantially axially of said tubes and having one end positioned in the hole through the inner of said tubes and having its other end positioned in the hole through the outer of said tubes, whereby electromagnetic movement of said tube of magnetic material in one direction rocks said lever about its pivot to move said tube of non-magnetic material in the opposite direction.

9. A counterbalanced armature structure for an electromagnet of the type having a hollow coil comprising, a guide post fixed to the frame of the electromagnet and extending therefrom into the central space in its coil, a first tube of magnetic material, a second tube positioned coaxially thereof, the inner one of said tubes being slid ably fitted over said guide post, and a lever pivoted substantially centrally of said tubes to said guide post and connected at one end to one of said tubes and at its other end to the other of said tubes, whereby sliding of said first tube in one direction rocks said lever about its pivot to slide said second tube in the opposite direction.

10. A counterbalanced armature for an electromagnet of the type having a hollow coil comprising, a guide post fixed to the frame of the electromagnet and extending therefrom into the central space in said coil, a tube of non-magnetic material slidably fitted over said guide post, a tube of magnetic material slidably fitted over said tube of non-magnetic material, and a lever pivoted sub stantially centrally thereof to said guide post and bearing at one end against said tube of magnetic material and at its other end against said tube of non-magnetic material, whereby sliding of said tube of magnetic material in one direction rocks said lever about its pivot to slide said tube of non-magnetic material in the opposite direction to balance movement of one tube by opposite movement of the other.

11. A counterbalanced armature for an clectromagnet having a hollow coil comprising, a guide post fixed to the frame of the electromagnet extending therefrom axially into the central space in said coil, said guide post having at its end farthest from its fixation to the frame a central tongue having a hole therethrough outwardly tapered from its center to each end thereof; a tube slidably fitted over said guide, said tube having a hole therethrough of substantially the size of the hole through the tongue of said guide and tapered outwardly from its inner end to its outer end, said tube also having a longitudinal slot therein diametrically opposite to its hole; a cup of magnetic material slidably fitted over said tube, said cup having an outwardly tapered hole therethrough positioned to register with the slot in said tube, the weight of said cup being such as to counterbalance said tube; and a lever extending through the hole in said guide and through the slot in said tube with its ends in the holes in said tube and said cup; whereby sliding of said cup rocks said lever in the hole in said guide and slides said tube oppositely.

Fessenden Llan. 12, 1915 Kuhn June 28, 1949 

